In recent years, there has been a tendency toward frequent use of structural members and the like made of difficult-to-cut materials such as titanium, and the number of situations in which such difficult-to-cut materials are cut has been increasing. In the machining of such difficult-to-cut materials, cutting inserts including chip breakers intended for stainless steel are exclusively used.
In the process of cutting stainless steel, a cutting insert disclosed by PTL 1 listed below or a cutting insert disclosed by PTL 2 listed below, for example, are used.
The cutting insert disclosed by PTL 1 includes a flat land for edge reinforcement that is provided on a rake face extending along a cutting edge. The land has a width of about 0.15 to 0.25 mm. The cutting insert further includes a breaker flute that is continuous with the land, and a breaker projection that is provided between the breaker flute and a central land portion of the cutting insert.
The cutting insert disclosed by PTL 2 includes a breaker flute provided in each of rake faces that intersect a flank face at acute angles, respectively, and a breaker projection provided between the breaker flute and a central land portion of the cutting insert.
In a case where the latter cutting insert is used for the machining of stainless steel, a rake face having a rake angle of smaller than 20° and a width of about 0.5 mm at most is provided along the cutting edge. Furthermore, a breaker flute having an inclination of larger than 20° C. is provided at a terminal end (a side that is Farther from the cutting edge is regarded as the terminal end) of the rake face.